1. Field of the Invention
The invention relates to a method and an apparatus for producing high dynamic range (HDR) pictures. The invention also relates to advantageous exposure apparatuses for use in a method such as this and an apparatus such as this.
2. Background Information
In photography and image processing, HDR image production or else dynamic range increase—or DRI technology—is known as a method by means of which a new image with a very high contrast ratio can be produced algorithmically from a series of differently exposed individual images (exposure series).
HDR image production, alternatively also referred to as dynamic range increase technology, is used in digital photography, in order to widen the dynamic range of an image.
The aim of the HDR image production method or the DRI method is to map the overall contrast of a motif with major brightness differences on an image and thus to obtain as many details as possible, or all details, using a plurality of images with a narrower contrast range than that of the original motif as a source.
In this case, a plurality of recordings of exactly the same image detail are made using different exposure times. This results in overexposed points in the recordings which have been exposed for longer times, but which allow even weakly illuminated areas to be seen. In contrast, the bright points can be seen such that they can be differentiated in the recordings with the shorter exposure times while, however, the poorly illuminated areas are black.
These individual recordings are subsequently combined using an image processing program, with the brightest points in a recording in each case being replaced by those from the next darker recording. This results in an image which can reflect a wider contrast range, and in which both the brightest and the darkest points can be seen in their structure.
In general, scenes with objects which have moved or are moving present difficulties, for example running people or animals, fluttering flags, etc.
By way of example, recordings with exposures of 1/125 seconds, 1/60 seconds, 1/30 seconds, 1/15 seconds etc. are taken in order to produce an exposure series of successive recordings. The large amount of time which is required to produce the exposure series in this way results in the following restrictions to the method:                The imaged scene must be static.        The scene must not, for example, have any moving objects or objects whose shape is changing (people running, plants in the wind, waves etc., are generally difficult).        The camera must be installed statically, for example mounted on a stand.        